Browsing by Subject "Self assembly"
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Item Directing and characterizing silicon nanocrystal self-assembly(2018-08-08) Guillaussier, Adrien Camille; Korgel, Brian Allan, 1969-; Milliron, Delia; Truskett, Thomas; Ellington, Andrew; Downer, MichaelSilicon nanocrystals or quantum dots are non-toxic and exhibit unique size tunable opto-electronic properties. Their bright photoluminescence as well as their ability to generate more than one electron per photon absorbed make them good candidates for both bioimaging and photovoltaics applications. Their surface can be functionalized with different ligands that protect them against oxidation and allow them to be dispersed and stable in a variety of solvents. Dodecane capped silicon nanocrystals can be dispersed in non-polar solvents such as hexane, chloroform or toluene for years without aggregating nor losing their optical properties. When deposited on a substrate under certain conditions, dodecane capped silicon nanocrystals can self-assemble into 2D or 3D periodic arrays of quantum dots called superlattices. These ordered structures of nanocrystals can potentially enhance the conductivity of the nanocrystal thin film which would be helpful for photovoltaic applications. In order to perform charge transport measurements through superlattices, large uniform ordered nanocrystal films must be achieved. Two deposition processes are studied and optimized to lead to the formation of several microns large both 2D and 3D silicon nanocrystals superlattices. A model is developed to understand the superlattice growth mechanism and several parameters are found to influence the superlattice morphology. Silicon nanocrystals can also be functionalized with chromophores to enhance their optical absorption. This can improve efficiencies of self-assembled quantum dots solar devices. Silicon nanocrystals functionalized with pyrene units are studied using transient absorption spectroscopy. They exhibit enhanced optical absorption and efficient carrier multiplication via energy transfer from the pyrene unit to the nanocrystal core. Finally, carboxylate terminated silicon nanocrystals are stable in water over a wide range of pH which makes them suitable for self-assembly in aqueous media. Incorporating biological receptor-substrate sites to the nanocrystal surface can permit recognition-driven self-assembly. Carbodiimide activation is commonly used to biofunctionalize nanoparticles. This chemistry is tested to attach an amine terminated PEG (polyethylene glycol) molecule to silicon nanocrystals. PEG functionalization is found to improve silicon nanocrystal photoluminescence stability.Item Lithographic patterning of polymeric media for biotechnology applications(2013-12) Deschner, Ryan Phillip; Willson, C. G. (C. Grant), 1939-; Ellington, Andrew; Ellison, Christopher; Bonnecaze, Roger; Korgel, BrianLithographic patterning has heavily utilized in the semiconductor industry for its ability to pattern vast numbers of complex shapes down to the nanometer scale. However, only recently has this technology been employed in the biotechnology field despite the fact that most of that the most important biological components such as cells, antibodies, DNA and proteins operate at this level. This work is an exploration of the use of lithographic printing methods in two areas deeply-entrenched in biotechnology: self assembly and microarray-based manipulation of biological media. It was inspired by the natural self assembly which occurs in nature and in our bodies at all scales. The majority of this work dealt with the patterning of bioreactive copolymers into different three-dimensional microshapes which could be functionalized with single strands of DNA for subsequent sequence-specific particle assembly. This type of technology, where very small-scale matter can be directed to self assembly into programmed macrostructures in a highly-specific manner has the capability to be adapted for many next-generation applications in drug delivery, nanofabrication, biosensing, and microelectronics. A secondary technology was explored in this work involving the paired sequencing of antibody gene sequences with the aid of lithographically-patterned microarrays. This methodology represents a bridging of bottom-up fabrication methods of DNA and proteins with top-down optical fabrication techniques which is already finding increasing utility in applications such as vaccine discovery, diagnostics, and autoimmune research. Because of the versatile nature of the components of this research, it is the hope of the author that the techniques discovered and explored here provide support and inspiration for future research in the biotechnology field as well as in other fields which may benefit as well.